Electrical sound device having unitary plastic base



Jan. 28, 1969 .1. DOGGART 3,425,057

ELECTRICAL SOUND DEVICE HAVING UNITARY PLASTIC BASE Filed June 5, 1965 Sheet of 5 A? I $4 /a I L 5/ J u "'3 J E I a /6 45 26 E 21 A922 42/ E JZJ' f/Gh? 5 .26 27 I E 1% -24 A" "56 /2 fez; 47

run Euros Jb/ N Doe's-4 5v cJaww/"W ATTORNEYS Jan. 28, 1969 .1. DOGGART 3,425,057 ELECTRICAL SOUND DEVICE HAVING UNITARY'PLASTIC BASE Filed June a, 1965 Sheet Z of 5 //V l/E N TOE JZJHN 2066A I? 7' %wx/Mz1w- .4 TTOENE Y5 Jan. 28, 1969 J. DOGGART 3,425,057

ELECTRICAL SOUND DEVICE HAVING UNITARY PLASTIC BASE Filed June 3, 1965 Sheet 3 of 5 INVENTOB Jo /v P066427" roe/vars United States Patent 23,260/64 US. Cl. 340 3ss Int. Cl. G10k 9/14 7 Claims ABSTRACT OF THE DISCLOSURE An electrical sound generator comprised of elements mounted upon a monoplastic base member. The base member includes a main portion which supports a magnetic element; and a secondary portion which supports a coil and magnetic core and striker. The main portion and secondary portion are joined by a resilient strip or hinge whereby the striker is normally spaced from the magnetic element and is moved into contact with the magnetic element when the coil is energized. A cover fits over the main portion of the base, having at least a portion thereof forming a diaphragm with a movable portion in contact with the magnetic element.

This invention relates to electrical sound generators.

According to the invention there is provided an electrical sound generator comprising a base which includes a main portion and a secondary portion which is formed integrally with the main portion and which is connected by a hinge to the main portion for movement relative thereto, the generator further comprising an element of magnetic material of low retentivity fixed to the main portion, a coil, and a core for the coil which core is formed from magnetic material of low retentivity and is mounted on the secondary portion for movement therewith, a striker part mounted on the secondary portion for movement therewith, a fixed part fixed on the main portion, the secondary portion being resiliently biased to a normal position in which the striker part is spaced from the fixed part, the arrangement being such that on energisation of the coil the striker part is moved from its normal position to strike said fixed part and on de-energisation of the coil, the striker part is released for return to its normal position. The core preferably provides said striker part and the element preferably provides said fixed part. To increase the sound generated, a diaphragm is preferably arranged to be moved by the striking of the striker part on the fixed part. In a convenient arrangement, a movable portion of the diaphragm bears on the side of the element opposite to the side which is to be struck by the striker part. The diaphragm preferably forms at least a portion of a cover for fitting on the main portion of the base.

The hinge preferably has a section narrower than the sections of the main portion and the secondary portion. The base is preferably made from polypropylene.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:

FIGURE 1 is an underplan view of a buzzer.

FIGURE 2 is a section on line 2-2 of FIGURE 1,

FIGURE 3 is a section on line 3-3 of FIGURE 1,

FIGURE 4 is a section on line 44 of FIGURE 1,

FIGURE 5 is a section on line 55 of FIGURE 1,

FIGURE 6 is a side elevation, partly cut away, of 70 the buzzer of FIGURE 1,

Patented Jan. 28, 1969 FIGURE 7 is a plan view, partly cut away, of the buzzer of FIGURE 1, and

FIGURE 8 is a section on line 88 of FIGURE 2.

Referring to the drawings, an electric buzzer comprises a circular base 11 moulded from polypropylene having a down-turned peripheral rim 12. An arcuate slot 13 is formed in the base 11 coaxially therewith and extending through about 280. The ends of this arcuate slot 13 respectively merge into two short parallel straight slots 14 which extend towards but end short of the periphery of the base 11. The part 10 of the base 11 in which the slots are formed is raised slightly relative to the surrounding substantially annular portion 15 of the base, the step on the base leading to this raised portion being in effect an upstanding rim 16 on the inner periphery of the annular portion 15. The portion 17 surrounded by the arcuate slot 13 has a downwardly extending peripheral rim 18 and a central opening 19. The rim 18 is divided into four quadrants by gaps for components to be described below. Surrounding the opening 19 is a tubular member 20 integral with the portion 17 leading upwardly from the portion 17 to an upper centrally apertured disc member 21. The portion 17, tubular member 20 and disc member 21 serve as a bobbin 22 on which a coil 23 is wound. The thickness of the part 24 betwen the parallel straight slots 14 is such that this part 23 acts as a resilient hinge. The part 24 is moulded with a thickness less than those of the partings 5 and 17. After moulding the first few flexings orient the molecules of polypropylene to form a strong hinge.

A soft iron core 25 of cylindrical form extends through the tube 20. The core 25 has an enlarged striker head 26 which rests on the top of the disc member 22. A soft iron armature plate 27 is fixed to the bottom of the core 25 and extends through gaps in two opposite sides of the downturned rim 18. This armature plate 27 extends beyond the bobbin rim 18 almost to the up-turned rim 16 of the annular portion 15 (see FIGURE 3). The core 25 and the armature plate 27 form an inverted T-shaped armature for the coil 23 wound on the coil bobbin 22.

A soft iron 'U-shaped frame 28 inverted over the bobbin is fixedly mounted on the base 11. The ends of the arms 29 of the U frame 28 are the same distance above the ends of the armature plate 27 as the centre of the frame 28 is above the head 26 of the core 25. The ends of the arms 29 of the frame 28 have lugs 31 which retain them in inwardly extending brackets 32 formed at the top of the upstanding rim 16.

Three terminals are mounted on the annular portion of the base and each comprises a self-tapping screw.

The first screw terminal 33 passes through a terminal strip 34 With ends up-turned beside the screw head to aid the retention of external connecting wires. The second terminal 35 is between the periphery of the base and the part 24 between the slots 14, and its screw retains a phosphor bronze contact strip 37. This strip 37 extends through a slot 38 in the part 24 and through gaps in the rim 18 to the other side of the portion 17 and is fastened under the armature plate 27. The third terminal 39 is diametrically opposite the second 35 and its screw retains a second phosphor bronze contact strip 41 extending a short distance under the first 37. The sides 42 of the second strip 41 are bent up beside the screw to aid retention of external connecting wires. The opposing faces of the strips 37, 41 are formed with silver contacts 43. A spring blade 44 is mounted under the bobbin 22 over the contacts 43, projecting into a slot 45 in the rim 16. The resilience of the blade 44 aids the natural resilience of the hinge 26 to bias the plate 27 and frame 28 apart.

The coil 23 is wound with enamelled copper wire on the bobbin 22, the ends of the wire being connected to the first and second terminals 33, 35 respectively.

A cruciform fibre disc 46 fits inside the down-turned rim 16 of the base to cover the underside of the components.

A tapered cover 47 of circular section can be secured on to the base to enclose the components of the buzzer.

The cover has two inwardly-directed retaining lugs 48 which fit into helical slots 49 in the base. The inner surface of the cover has a projection 51 at its centre which bears on the U-shaped frame 28.

The base has two fixing holes 52 for fixing screws and a wiring hole 53 for wires to the terminals. The rim of the base 18 has a knock-out portion 54 adjacent the wiring hole 53 for the entry of surface mounted wires.

Direct or alternating current may be supplied to the first 33 and third terminals 39 on the base 11 to operate the buzzer. When the coil 23 is energised, the soft iron core 25 and the armature plate 27 will be magnetised and will be attracted to the U-shaped frame 28. The attraction flexes the hinge 24 of the base 11 so that the core 25 moves to strike the frame 28. As the hinge 24 flexes, the contact strip 37 fixed to the core 25 is moved out of contact with the second contact strip 41 and the coil 23 is de-energised.

On de-energisation, the coil 23 and its core 25 are no longer attracted to the frame 28 and return to their original position due to the resilience of the hinge 24 and of the blade 44. When the contact strips 37, 41 move into contact again, the procedure repeats itself as long as current is supplied to the first and third terminals 33, 39.

The cover 47 having its projection 51 bearing on the soft iron frame 28 acts as a diaphragm to broadcast the impulses of the core 25 striking the frame 28.

In an alternative arrangement, alternating current is supplied to the first and second terminals 33, 35, that is, directly to the ends of the coil 23, The coil 23 is then energised twice per cycle of the alternating current, and the frequency of the impulses is twice that of the alternating current.

I claim:

1. An electrical sound generator comprising a monoplastic base member including a main portion and a secondary portion connected by a resilient hinge;

an element of magnetic material mounted upon said main portion;

an electrical coil and magnetic core mounted upon said secondary portion for movement therewith;

a striker fixed to said magnetic core, normally spaced from said element; and

means for energizing said coil whereby said striker is moved into contact with said element.

2. An electrical sound generator comprising a monoplastic base member including a main portion formed with an opening in the center thereof and a secondary portion suspended within said opening by a resilient hinge;

an element of magnetic material mounted upon said main portion;

an electrical coil and magnetic core mounted upon said secondary portion for movement therewith;

a striker fixed to said magnetic core, normally spaced from said element; and

means for energizing said coil whereby said striker is moved into contact with said element.

3. A generator as described in claim 1 further including a diaphragm attached to said base to be moved by the contact of said striker with said element.

4. A generator as described in claim 2 including a diaphragm mounted on said base having a resiliently movable portion bearing upon the side of the element opposite to the side which is to be struck by the core.

5. A generator as described in claim 2 including a cover fitting over the main portion of said base, at least a portion of the cover forming a diaphragm having a resiliently movable portion bearing on the side of the element opposite to the side which is to be struck by the core.

6. A generator as described in claim 1 wherein the resilient hinge has a cross section narrower than the cross section of the main portion and secondary portion.

7. A generator as described in claim 1 wherein said base is formed of polypropylene.

References Cited UNITED STATES PATENTS 1,516,260 11/1924 Wood 340388 1,667,206 4/1928 Kersten 340-388 JOHN W. CALDWELL, Primary Examiner.

H. PITTS, Assistant Examiner.

US. Cl. X.R. 

